背景:胎儿腹围异常的诊断基于>90百分位数或<10百分位数。有几十种既定的标准可以用来确定给定腹围测量的百分位数,但是没有确定的方法来确定应该使用哪些规范。
目的:本研究旨在评估5个既定腹围规范对我们测量的适用性,如果有的话,应用于胎儿腹围异常的诊断。
方法:收集来自6个母胎医学实践的数据进行横断面研究。纳入标准是在妊娠22.0至39.9周时有心脏活动的单胎胎儿,完整的胎儿生物测量,从2019年或2020年开始考试。对于在研究期间进行超过1次合格检查的患者,随机选择一项单一检查纳入.研究了五个腹围标准:Hadlock公式,世界卫生组织的胎儿生长曲线,21世纪项目国际胎儿和新生儿生长联盟;和美国国立儿童健康与人类发展研究所胎儿生长研究(白人患者的胎儿和统一标准)。使用腹围与胎龄相关的公式,我们计算了腹围的z得分(与平均值的标准偏差),z分数的标准偏差,Kolmogorov-SmirnovD统计,和相对均方误差。根据6个标准评估了5个标准是否适合我们的数据:平均z得分接近0,z得分的标准偏差接近1,低D统计量,低均方误差,分数>90百分位数接近10%,和分数<10%的值接近10%。
结果:在15,042例患者的40,684例超声检查中符合纳入标准。考虑到6个评价标准,观察到的腹围最符合世界卫生组织的标准(平均z评分为0.11±1.05,D统计量为0.041,均方误差为0.84±1.46,13%的检查>90百分位数,7%的考试<10%)。Hadlock参考在其恒定标准偏差的假设中存在异常,导致早期胎龄异常值的诊断不足,晚期胎龄过度诊断。21世纪项目标准的国际胎儿和新生儿生长联盟的平均周长小于所有其他标准,导致小圆周的诊断不足和大圆周的过度诊断。当将分析限制在5487次检查的低风险亚组时,观察到类似的结果,而没有确定胎龄大或胎龄小的风险因素。
结论:腹围异常的诊断取决于用于定义腹围百分位数的规范。世界卫生组织的标准最适合我们的数据。
BACKGROUND: The diagnosis of abnormal fetal abdominal circumference is based on values >90th or <10th percentile. There are dozens of established norms that can be used to determine the percentile of a given abdominal circumference measurement, but there is no established method to determine which norms should be used.
OBJECTIVE: This study aimed to evaluate the applicability of 5 established abdominal circumference norms to our measurements and to determine which, if any, should be used for the diagnosis of abnormal fetal abdominal circumference.
METHODS: Data were pooled from 6 maternal-fetal medicine practices to conduct a cross-sectional study. The inclusion criteria were a singleton fetus at 22.0 to 39.9 weeks of gestation with cardiac activity present, complete fetal biometry measured, and examination from 2019 or 2020. For patients with >1 eligible examination during the study period, a single examination was chosen at random for inclusion. Five norms of abdominal circumference were studied: the Hadlock formula, the World Health Organization Fetal Growth Curves, the International Fetal and Newborn Growth Consortium for the 21st-Century Project; and the National Institutes of Child Health and Human Development Fetal Growth Studies (fetuses of White patients and unified standard). Using formulas relating abdominal circumference to gestational age, we calculated the z scores of abdominal circumference (standard deviations from the mean), standard deviation of the z score, Kolmogorov-Smirnov D statistic, and relative mean squared error. The 5 norms were assessed for fit to our data based on 6 criteria: mean z score close to 0, standard deviation of the z score close to 1, low D statistic, low mean squared error, fraction of values >90th percentile close to 10%, and fraction of values <10th percentile close to 10%.
RESULTS: The inclusion criteria were met in 40,684 ultrasound examinations in 15,042 patients. Considering the 6 evaluation criteria, observed abdominal circumferences had the best fit to the World Health Organization standard (mean z score of 0.11±1.05, D statistic of 0.041, mean squared error of 0.84±1.46, 13% of examinations >90th percentile, and 7% of examinations <10th percentile). The Hadlock reference had an anomaly in its assumption of a constant standard deviation, resulting in the underdiagnosis of abnormal values at early gestational ages and overdiagnosis at late gestational ages. The International Fetal and Newborn Growth Consortium for the 21st-Century Project standard had a mean circumference smaller than all the other norms, resulting in the underdiagnosis of small circumferences and the overdiagnosis of large circumferences. Similar results were observed when restricting the analyses to a low-risk subgroup of 5487 examinations without identified risk factors for large for gestational age or small for gestational age.
CONCLUSIONS: The diagnosis of abnormal abdominal circumference depends on the norms used to define abdominal circumference percentiles. The World Health Organization standard had the best fit for our data.